Omission of adjuvant therapy in stage I clear cell ovarian cancer: Review of the BC Cancer experience

BACKGROUND: Since 2012, the BC Cancer provincial treatment guideline for surgically staged stage IA/B and IC1 (defined by intraoperative rupture only) clear cell ovarian cancer (CCOC) has been to offer observation only. We reviewed the clinical outcomes of all stage I CCOC patients since policy implementation. METHODS: A retrospective, population-based cohort study of all stage I CCOC patients operated on between April 2012 and December 2017 was conducted. Patient, tumor, surgical and clinical outcome data were collected. Survival analysis was conducted using Kaplan-Meier methods. RESULTS: 78 patients with stage I disease were identified. 40 patients with stages IA/B and IC1, who underwent post-operative observation, were included in the analysis. Lymph node dissection was omitted in 20 patients (50%). Median duration of follow-up was 36 months. There were 4 recurrences (10%), 3 metastatic. The 5-year disease-free survival is 90%, and the 5-year overall survival is 95% for stage IA/B and 90% for stage IC1 (p = 0.645). In comparison, 5-year overall survival for stage IC2 (surface involvement) and IC1 with sharp dissection (all received adjuvant chemotherapy) is 82% (p < 0.001) and for stage IC3 (positive washings) was 23% (p < 0.001). CONCLUSION: Adjuvant therapy can be safely omitted in patients with stage I A/B and IC1 CCOC. Recurrence rates are low and survival is >90% at 5 years. Stage IC2 /IC3 had worse outcomes, thus stage I substage is instrumental in predicting clinical outcomes for CCOC. Lymph node metastases are rare in stage IA/B/C1 CCOC as absence of lymphadenectomy did not increase the risk of disease recurrence.